The present invention relates to call tariff determination in mobile telecommunication networks and more particularly to the determination of call tariffs for provision to an access network in respect of a roaming mobile telephone subscriber.
In today""s competitive mobile telephone market, in order to attract new customers operators are offering a diverse range of payment options. In addition to the conventional payment scheme where a subscriber is billed regularly for telephone calls made over a period immediately preceding the issuing of a bill, there is for example the prepaid card schemes where a user purchases a card and then uses a secret number provided on the card to top-up an account maintained by his operator. The user is able to make and receive calls until such a time as the balance in his account falls to zero. The account must be topped-up using a new prepaid card before the user can make and receive calls once more. Many new services are also being introduced by mobile telephone operators to attract new customers as well as to maintain their existing customer base. One such service which is in limited current use is known as xe2x80x9cAdvice of Chargexe2x80x9d and allows mobile telephone""s to be provided with call charge information during the call set-up phase to enable call charges to be computed by the telephone either during or after a call.
In a mobile telecommunications network, there is usually present a node which controls charging for subscribers of that network. This xe2x80x9cchargingxe2x80x9d node maintains details of the tariffs charged by the operator for the complete range of call options, e.g. home mobile telephone to home mobile telephone, home mobile telephone to other national telephones, international tariffs, etc. Providing that a subscriber""s telephone is registered with the home network, there is in principal no bar to providing services such as Advice of Charge and to controlling and monitoring in real time prepaid card subscribers and the like, as all the necessary information is available at the home network""s charging node (or can be readily obtained by that node). Problems arise however when a mobile telephone subscriber is not at home but rather is registered with some foreign mobile telephone network (the term xe2x80x9caccessxe2x80x9d network is used below to describe the network to which a subscriber is directly connected).
Such a foreign access network will have its own charging node which must be able to determine real time charging information for a roaming subscriber if prepaid subscribers are to be allowed to roam, or if services such as Advice of Charge are to be available to roaming subscribers. Indeed this may be necessary whenever subscribers have a credit ceiling which must not be exceeded.
The inventor of the present invention has realised that there is at present no mechanism by which a charging node of a foreign network can accurately calculate the tariff to be applied to a roaming subscriber. This is because the tariff is typically made up of a component from the foreign network as well as a component from the subscriber""s home network. At present, there is no means by which the foreign network can be made aware of the home network""s tariff component.
It is an objective of the present invention to overcome or at least mitigate the above noted disadvantages of existing and currently proposed solutions for enabling a call charging node of a foreign network to determine the call tariff for a roaming mobile subscriber.
According to a first aspect of the present invention there is provided a method of providing call charge information in a mobile telecommunications system, the method comprising:
maintaining in a home mobile telecommunications network a set of call charging algorithms which correspond to respective foreign mobile telecommunications networks; and
periodically transferring the algorithms to respective foreign networks,
wherein the transferred algorithms may be used by the receiving foreign networks to calculate call charge information for subscribers of the home network when they are roaming in the foreign networks.
It will be appreciated that the terms xe2x80x9chomexe2x80x9d and xe2x80x9cforeignxe2x80x9d may be used interchangeably to describe mobile networks, i.e. for some subscribers a network will be a home network whilst for others it will be a foreign network.
Embodiments of the present invention provide charging information required by foreign networks to calculate call charges for roaming subscribers in real time or near real time, whilst requiring only a relatively small volume of inter-network signalling traffic. The volume of signalling traffic is certainly less than would be required, for example, if a charging algorithm were to be transferred for each subscriber or for each call initiated in a foreign network by a roaming subscriber.
The charging algorithm transferred to a foreign network may be used by that network to determine a call tariff for subscribers of the home network. For example, the charging algorithm may comprise a multiplying factor by which the foreign network multiplies its own charge.
Within the home network, said set of call charging algorithms may be maintained at a rating node. The algorithms transferred to the foreign networks may be received by charging nodes of those networks. The charging nodes of the foreign networks may be associated (e.g. co-located) with respective switches. In the case of GSM and UMTS mobile telecommunications networks, these switches may be Mobile Switching Centres (MSCs).
In certain embodiments of the present invention, a charging algorithm is sent to a foreign network upon receipt at the home network of a polling message from the foreign network. Polling messages may be sent by the foreign network at regular intervals. It will be appreciated that a foreign network may have agreements with many other networks, and will poll each of those networks separately to obtain up to date charging algorithms. The foreign network may only pole those networks having a subscriber currently registered with the home network, thus reducing signalling traffic.
In other embodiments of the present invention, the home network may maintain a register of foreign networks (or foreign network charging nodes) with whom it has a roaming agreement. When a new foreign network or foreign network charging node is brought into service, that network or node registers with the home network whereupon the home network transfers the appropriate charging algorithm to the foreign network. The foreign network is notified of subsequent changes to the algorithm.
The home network may maintain for one or more of the charging algorithms maintained by it, a time and date when the receiving foreign network(s) should activate the charging algorithm(s).
The home network may maintain one or more secondary charging algorithms associated with respective ones of said set of charging algorithms, together with respective activation times and dates. The secondary algorithms and the activation times and dates are transferred to the foreign networks together with the primary algorithm. A receiving foreign network will replace the primary algorithm with the secondary algorithm at he activation time and date.
According to a second aspect of the present invention there is provided apparatus for providing call charge information in a mobile telecommunications system, the apparatus comprising:
a rating node for use in a home mobile telecommunications network and arranged to maintain a set of call charging algorithms which correspond to respective foreign mobile telecommunications networks;
charging nodes for use in respective foreign networks to calculate call charges for subscribers of the home network roaming in the foreign networks; and
transfer means associated with said rating node for periodically transferring the algorithms to respective foreign network charging nodes,
wherein the transferred algorithms may be used by the receiving foreign networks to calculate call charge information for said roaming subscribers.